The present invention relates to corrugating converting machinery, more particularly to equipment for the dosing of various desired additives to the corrugating adhesive used in the manufacture of corrugated board.
Corrugated paper board is commonly prepared by first forming a corrugated element or core by passing a cellulosic sheet between corrugating rolls forming a substantially sinusoidal or serpentine cross-section in the sheet. An adhesive is commonly applied to the tips of the thus formed sinusoidal portion called flutes and a noncorrugated or planar cellulosic liner is applied against the adhesive coated flutes of the corrugated elements as the corrugated sheet passes between a corrugating roll and a pressure roll. The resulting paper product having the corrugating medium on one side and the planar liner on another side is called a single-faced element. The single-faced element may be used as is in certain applications as a liner or buffer material within a container. More commonly adhesive is applied to the flute tips of the single-faced element and a second liner sheet is subsequently applied to the adhesive liner in a xe2x80x9cdouble facerxe2x80x9d operation. The second liner sheet is exposed to conditions of heat and pressure during its contact with the adhesive. In practice, the sheet of corrugated cardboard most frequently encountered has two plane sides placed on each side of the corrugated core. Depending on the specific strength desired, a sheet of corrugated cardboard may also be provided with a more complex structure, such as two corrugated cores and three plane surfaces, two outer ones and one inner one separating the two corrugated cores. This is referred to as double wall board.
Starch-based adhesives are most commonly used in the corrugating process due to their desirable adhesive properties, low cost and ease of preparation. The most fundamental of starch corrugating adhesives is an alkaline adhesive which is comprised of raw, ungelatinized starch suspended in an aqueous dispersion of cooked starch. The adhesive is produced by gelatinizing starch in water with sodium hydroxide (caustic soda) to yield a primary mix of gelatinized or cooked carrier, which is then slowly added to a secondary mix of raw (ungelatinized) starch, borax and water to produce the full-formulation adhesive. In the corrugating process, the adhesive is applied (usually at between 25xc2x0 and 55xc2x0 C.) to the tips of the fluted paper medium or single-faced board, whereupon the application of heat causes the raw starch to gelatinize, resulting in an instantaneous increase in viscosity and formation of the adhesive bond.
The typical corrugating process and the operation and use of corrugators in general are described in U.S. Pat. Nos. 2,051,025 and 2,102,937 issued on Aug. 18, 1936 and Dec. 21, 1937, respectively, to Jordan Bauer.
In addition to starch, caustic, borax and water, various additives have been used to modify the properties of the adhesive an/or the resulting corrugated cardboard. Such additives include preservatives, water resistance additives, defoamers, colorants, wetting agents, urea and performance additives that increase tack or rate of green bond formation. For example, corrugating adhesives can be rendered moisture resistant or water-resistant by the addition of materials such as ketone aldehydes. These materials cross-link the starch molecules making it more difficult for water to dissolve the starch. Urea appears to hold moisture at the glue line and helps improve bonds, particularly at the single facer. The above-described additives are typically post-added to the formulated water-starch-caustic-borax-containing corrugating adhesive in order to obtain or enhance certain properties.
It would be desirable to have methods and means to add a desired component in a predetermined amount to a corrugating adhesive and to monitor how much component is added, how much has been used, how much remains, and when stock is in need of replenishment/reorder. The current invention fulfills this need.
The invention is directed to a corrugating adhesive system comprising at least one adhesive storage tank where prepared adhesive is stored prior to use, at least one day tank, a means for adding a predetermined amount of a predetermined additive to a predetermined day tank for delivery to a predetermined area of the corrugator, and a means for recycling the adhesive from the corrugator back to the day tank or, alternatively, back to the storage tank.
One embodiment of the invention provides a corrugating system comprising a corrugating apparatus containing at least a single facer machine, a storage tank for storing a formulated adhesive, a day tank for holding a predetermined amount of a formulated adhesive and a predetermined amount of at least one predetermined additive, a source of a predetermined additive, a means for moving a predetermined amount of said formulated adhesive from said storage tank to said day tank, a means for moving a predetermined amount of said additive from said source to said day tank, and a means for moving said additive-containing adhesive from said day tank to said corrugating apparatus. In response to movement of a predetermined amount of said formulated adhesive from said storage tank to said day tank, a predetermined amount of said predetermined additive is moved from the source of said additive to said day tank.
The corrugating systems of the invention will also comprise a means for recycling the adhesive from the corrugator back to the day tank and a means for recycling the adhesive from the corrugator back to the storage tank.
Typically, the corrugating system will comprise at least two day tanks, a source of a first additive and a source of at least a second additive. The source of the additive is not particularly limiting and may be a drum, a tote, bulk storage tank, or the like.
In a second embodiment, a computer integrated corrugating system is provided which system will preferably comprise a means for moving a predetermined amount of said formulated adhesive from said storage tank to said day tank in response to a signal indicating a need for replenishing said tank with adhesive, a means for moving a predetermined amount of said predetermined additive from said source to said day tank in response to a signal indicating a need to replenish said tank with additive. In preferred systems, a means to signal when a predetermined low amount of additive remains in said source is provided, as well as a means to reorder predetermined quantities of additive in response to said signal.